This invention pertains to recovery of petroleum from underground reservoirs and pertains in particular to the breaking of emulsions of crude oil and water that are recovered from a producing well of the reservoir.
Recovered liquid from a producing well can be in the form of oil and water emulsions which are quite stable, especially when they comprise a surfactant which was introduced into the reservoir for enhancing the recovery of crude oil therefrom, e.g. as during secondary and/or tertiary recovery processes. Accordingly, a surfactant can be introduced into the reservoir in the form of a solution or dispersion which is either miscible with the crude oil or else exhibits lower interfacial tension therewith. Following introduction of a surfactant, a drive water slug which has been thickened by means of a polymer, such as a polyacrylamide or Kelzan, can be injected into the reservoir for the purpose of displacing crude oil toward and through a producing well. Emulsion of the crude oil with water can thus be a result of mixture of the oil with water which was introduced into the reservoir as a carrier medium for the surfactant and/or for driving displaced crude oil toward a producing well.
There is presently an ascendancy of secondary and tertiary processes for recovery of petroleum since there is an ever increasing demand for oil and since more of such processes are now beginning to appear economically attractive. The favorable economics thereof will nonetheless be largely dependent upon the cost of breaking the oil and water emulsions that are consequently produced by these methods, and especially when a produced emulsion is rendered quite stable by consequential content of a surfactant, such as a petroleum sulfonate, that was introduced into a reservoir for the purpose of improving displacement and recovery of crude oil therefrom.
Broadly speaking, therefore, one object of the present invention is to provide an improved method for separating crude oil from water when these two fluids are recovered as a mixture from a petroleum reservoir.
Another object is to provide a method for separating crude oil from emulsions of crude oil and water.
Still another object is to provide an improved method of separating crude oil from emulsions of oil and water that are produced from a well in a petroleum reservoir.
Yet another object is to provide an improved method of separating crude oil from an emulsion which comprises crude oil, a surfactant and water.
Even another object is to provide a method for recovering crude oil from an emulsion of crude oil and water that is stabilized by a sulfonate.
A further object is to provide an inexpensive method of breaking emulsions of crude oil and water.
Other objects and advantages of the invention will become apparent from the following description and the appended claims.